Thermoelectric cooling apparatus



June 29, 1965 H. MULLER 3,191,391

THERMOELECTRIC COOLING APPARATUS Filed Jan. 5, 1962 2 Sheets-Sheet'lFig. 1

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June 29, 1965 H. MULLER v 3,191,391

THERMOELECTRIC COOLING APPARATUS Filed Jan. 3, 1962 2 Sheets-Sheet 2Fig. 3

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United States Patent 3,191,391 THERMOELECTRIC COOLING APPARATUS HeinzMiiller, Berlin-Charlottenburg, Germany, assignor toSiemeus-Electrogerate Aktiengesellschaft, Berlin, Germany, a corporationof Germany Fiied Jan. 3, 1962, Ser. No. 164,079 Claims priority,appligatliorsglermany, Jan. 6, 1961, 1

8 Claims. (or. 62-3) My invention relates to cooling apparatus, such asrefrigerator cabinets, in which the cold-producing devices consist ofbatteries or blocks of thermocouples traversed, when in operation, byelectric current to lower in each couple the temperature of one junction(cold junction) relative to the temperature of the other junction (hotjunction).

The efiiciency of such Peltier blocks is effected by detrimental heatlosses due to direct heat exchange between the cold-junction side andthe hot-junction side of the block. In order to minimize such heatlosses it has been proposed to mount the Peltier blocks, each comprisinga multiplicity of thermocouples and interconnecting metal conductors orbridge pieces, into a vacuum container. Devices of this type, however,encounter difficulties if the vacuum jacket of the vessel extends closeto the Peltier block because then the cold-junction may be subjected toheating from the hot-junction side particularly since the distancesbetween hot side and cold side in most cases are relatively short.

It is an object of my invention, therefore, to provide a Peltier coolingapparatus, employing a vacuum container, in which the detrimental heatflow is greatly reduced.

To this end, and in accordance with a feature of my invention, the heatexchange on the hot side and on the cold side of the Peltier block iselfected by means of respective circulation systems which contain aflowing heattransfer medium, preferably a liquid subjected toevaporation and condensation during its course of circulatory travel.The arrangement is such that the heat exchangers of both systems, whichare in direct heat exchange with the Peltier block, are locatedcompletely within the vacuum container together with the Peltier block,and only the circulation lines of the heat exchanging systems are inthermal contact with the wall of the vacuum container at thoselocalities where they pass through the wall.

As a result, and in accordance with another feature of my invention, thePeltier block can be built into a large area vacuum vessel, so that theheat flow from the hot to the cold side of the Peltier block can begreatly minimized. In the novel apparatus such a heat flow takes placeonly from the pipes of the heat exchanger system inserted into thevacuum container on the hot side of the Peltier block, to thecorresponding pipes appertaining to the heat exchanger system located inthe vacuum space on the cold side of the block, It is particularlyfavorable that the path between these two localities where the pipespass through the sheet metal of the vacuum housing is relatively long.It is, therefore, readily feasible and not detri mental, to directlyweld the pipes of the circulatory exchange, or lines at the wallintersection points, directly to the metal of the vacuum container. Thevacuum container is preferably made of stainless steel, for examplechrome-nickel steel. In this case the heat flow can be fur' ther reducedby using extremely thin sheets of steel since the. heat conductance ofthis material is small.

If it is desired to obtain a particularly effective reduction in heatflow between the pipe-entering localities of the vacuum housing, thepipes of the circulation lines can be inserted into the metallic wall ofthe vacuum vessel with the aid of an insulating intermediate layer, forexample a molten glass plug or sleeve. Another way of greatly reducingthe heat flow is to construct the wall of the vacuum container from anon-metallic material, particularly a synthetic plastic particularlysuitable for such purposes.

When employing the invention in conjunction with cabinets, containers orother cooling chambers surrounded by heat-insulating walls, thedimensions of the vacuum container can be adapted to the thickness ofthe insulating wall and a mounting opening left vacant in thatinsulating wall so that the vacuum container constitutes a closure andcover for the mounting opening and the walls of the vacuum containerform on both sides a continuation of the outer and inner surfaces on theinsulating wall and preferably substantially flush with the lattersurfaces. In this manner a good utilization of the available space isobtained because only the heat receiving and heat dissipating partsproper of the circulatory heatexchanger systems protrude out of theinsulating wall into the cooling chamber on the one hand and into theambient air on the other hand. The nipple for the connection of a pump,and the in-leads for the electric conductors to be connected to thePeltier block, in devices of the latter type, are preferably arranged onthe external wall of the vacuum container facing the hot side of theapparatus.

The foregoing and more specific features of the invention will beapparent from, and will be described in, the

following with reference to the drawing showing, by way of example, anembodiment of Peltier cooling apparatus.

according to the invention.

FIG. 1 shows schematically and in section a Peltier apparatus togetherwith part of an insulating wall structure in which the system ismounted;

FIG. 2 shows in perspective the Peltier block of the same apparatus; and

FIG. 3 shows a modified part of the Peltier apparatus of FIG. 1.

Like parts are identified by the same reference numerals in the figures.

Denoted by 1 and 1a are the thermoelectrically different legs of aPeltier thermocouple which are interconnected by electrically andthermally conducting bridge pieces 2 consisting, for example of copper.Each leg is further connected with the leg of an adjacent couple byanother bridge piece 2. In this manner a large number of thermocouplesare combined into a single Peltier block which will be more fullydescribed hereinafter.

The hot-junction side of the block is in contact with the pressure pot 3serving as an evaporator. The coldjunction side of the block isanalogously in contact with the planar wall of another pressure pot 4designed as a condenser. Both pressure pots may consist of stainlesssteel or any other suitable material of sufiicient strength. This is sobecause both are inserted into a vacuum container and the heat exchangebetween the Peltier couples and the environment is effected by theevaporating and recondensing liquids contained in the two heatexchanging systems of which the evaporator 3 and the condenser 4 formparts. The pressure pot 3 operating as evaporator is a component of theheat transfer system whose external air-cooled condenser is denoted by5. The appertaining circulatory linesof this system, consisting ofmaterial well suitable for welding or hard-soldering, for example steelor copper, are denoted by 6 and 7. The pressure pot 3 on the cold sideof the Peltier block, operating as condenser, forms a component of asecond heat transfer system which comprises an evaporator 8 located inthe internal evaporator of the refrigerator cabinet or other coolingchamber that is to be cooled by means of the thermoelectric apparatus.Both heat transfer systems operate on the principle of evaporating andcondensing a liquid coolant or refrigerant. By means of tensioning bolts12 the two pressure pots 3 and 4 are firmly stressed against each otherand against the Peltier block to form a good heat conducting contacttherewith.

The entire apparatus unit, constituted by the two pressure pots 3, 4 andthe intermediately located Peltier block is completely inserted into avacuum chamber 13 which is enclosed by the walls 14, 15 and 16 of avacuum container. A direct heat contact between the Peltier block andthe walls of the vacuum container in this embodiment exists only at thewelding locations 17 where the circulating pipes 6 and 7 are welded intothe upper wall 14, and at the corresponding welds 18 where thecirculating pipes 10, 11 enter through the lower wall 16 of the vacuumcontainer. Denoted by 19 is the external sheet-metal structure, and by20 the internal sheet-metal wall of a refrigerator cabinet. The spacebetween these two sheet-metal skins is filled with heat insulation 21consisting for example of glass wool. As mentioned, the coolerrefrigerating chamber within the cabinet is located beneath the wall 20to be cooled by the evaporator 8. The dimensions of the vacuum containerare adapted to the thickness of the cabinet wall structure and to thesize of a mounting recess 22 so that the vacuum container forms aclosure for the mounting recess 22 and its outer walls 14 and 16 aresubstantially flush with the outer and inner sheets 19 and 20 of thecabinet wall structure. The pump nipple 23 and an in-lead 24 for theelectric cable is located in the outer vacuum-container wall 14 facingthe hot-junction side of the Peltier block.

In the modification of FIG. 3, the circulating pipes 6, 7 and 10, 11instead of being welded to the vacuum containing walls 14 and 16,respectively, are inserted through insulating plugs or sleeves 25 ofglass, for example, that are mounted in openings in the walls.

' While the Peltier block is shown only schematically in FIGS. 1 and 3,details of its design are apparent from FIG. 2. The respectivelydifferent legs 1 and 1a of each couple consist of semiconductor bodiesof p-type and H- type material. Suitable, for example, as p-typematerial is a solid solution of bismuth telluride and antimonytelluride. Suitable as n-type material is a solid solution of bismuthtelluride and bismuth selenide. The top and bottom sides of each leg 1and 1a are made solderable by electroplating with copper or nickel or byvapor deposition of such metals, with or without simultaneousapplication of ultrasonics. The n-type and p-type semiconductor bodiesare all serially connected by the currentconducting bridge pieces 2 sothat all hot junctions face upwardly in the illustrated embodiment ofFIG. 1, and all cold junctions face downwardly. Connected to the firstand last semiconductor body of the entire block are terminal pieces 25and 26 to which respective electric leads are attached in order to passcurrent through the entire block.

It will be understood, however, that the particular choice of thematerials for the legs of the Peltier couples as well as the manufactureof the Peltier block as such, are not essential to the inventionproperand may be modified in various respects. For example, such othermaterials and manufacturing methods may be used as are described in US.Patent No. 2,978,570 and in the copending application Serial No.150,701, of W. Hanlein for Thermoelectric Battery and Method of ItsProduction, filed November 7, 1961.

It will also be obvious to those skilled in the art, upon studying thisdisclosure, that various modifications are applicable with respect todesign and arrangement of the components, and hence that the inventioncan be given embodiments other than particularly illustrated anddescribed herein, without departing from the essential features of myinvention and within the scope of the claims annexed hereto.

I claim:

1. Apparatus for thermoelectric cooling comprising a multiplicity ofelectrically interconnected thermocouples jointly forming a block havinga cold-junction side and a hot-junction side, two heat transferringcirculation systems each having a fluid-containing vessel joined indirect heat contact with said block at one of said respective sides forheat exchange with said block, a relatively thinwalled vacuum containerin which said block and said two vessels are mounted in spaced relationto the container walls, each of said two circulation systems havingfluid lines extending from one of said respective vessels through thecontainer wall to the outside thereof, whereby any heat contact withsaid container is limited to the passages of said lines through saidwalls.

2. Apparatus for thermoelectric cooling comprising a multiplicity ofelectrically interconnected thermocouples jointly forming a block havinga cold-junction side and a hot-junction side, two fluid circulationsystems containing an evaporable and condensable coolant and each havingan evaporator and a condenser and interconnecting fluid lines, theevaporator of one of said systems and the condenser of the other systembeing joined with said block in direct heat-conductive contact therewithon said two respective sides thereof for heat exchange with said block,a relatively thin-walled vacuum container, said block joined with saidlatter evaporator and said latter condenser being mounted in said vacuumcontainer in spaced relation to the container walls, said otherevaporator and said other condenser being disposed outside of saidcontainer, and said lines extending from within to without saidcontainer through said walls, whereby any heat contact with saidcontainer is limited to the passages of said lines through said walls.

v 3. Apparatus for thermoelectric cooling comprising a multiplicity ofelectrically interconnected thermocouples jointly forming a block havinga cold-junction side and a hot-junction side, two heat transferringcirculation systems each having a fluid-containing vessel joined indirect heat contact with said block at one of said respective sides forheat exchange with said block, a vacuum container having relatively thinmetal walls, said block and said two vessels being disposed in saidvacuum container in spaced relation to said walls, each of said twocirculation systems having fluid lines extending from one of saidrespective vessels through the container wall to the outside thereof,and said lines being fusion-joined with said walls at the locality wherethe lines pass through the walls.

4. In thermoelectric cooling apparatus according to claim 1, said vacuumcontainer comprising insulating inserts mounted in said walls andtraversed by said lines.

5. In thermoelectric cooling apparatus according to claim 1, said vacuumcontainer consisting of stainless chrome-nickel steel.

6. Apparatus for thermoelectric cooling comprising a cooling-chamberstructure having a heat-insulated wall and having an opening in andthrough said wall, a relatively thin-walled vacuum containersubstantially matching said opening and being inserted therein, saidcontainer forming a closure for said opening, a Peltier block comprisinga multiplicity of electrically interconnected thermocouples and having acold-junction side and a hot-junction side, two heat transferringcirculation systems each having a fluid-containing vessel joined indirect-heat contact with said block at one of said respective sides forheat exchange with said block, said block and said two vessels beingdisposed in said vacuum container in spaced relation from the containerwalls, and each of said two systems having fluid lines extending fromone of said respective vessels through the container wall to the outsidethereof.

7. In thermoelectric cooling apparatus according to claim 6, said coldand hot sides of said block being paral- 5 6 lel to the surfaces of saidheat-insulated wall, and'said References Cited by the Examiner vacuumcontainer having its outer and inner surfaces UNITED STATES PATENTSsubstantially flush with the outer and inner surfaces respectively ofsaid heat-insulated wall. 2,109,002 2/38 Warren 62.26? 8. Inthermoelectric cooling apparatus according to 5 2,947,150 8/60 Roeflerclaim 6, said vacuum container having a pump-connection 3,054,840 9/62Alsmg 62 '3 nipple and an electric-cable in-lead both located in thecontainer wall that faces said hot-junction side of said WILLIAM PrimaryExammer block. ROBERT A. OLEARY, Examiner.

1. APPARATUS FOR THEREMOELECTRIC COOLING COMPRISING A MULTIPLICITY OFELECTRICALLY INTERCONNECED THEREMOCOUPLES JOINTLY FORMING A BLOCK HAVINGA COLD-JUNCTION SIDE AND A HOT-JUNCTION SIDE, TWO HEAT TRANSFERRINGCIRCULATION SYSTEMS EACH HAVING A FLUID-CONTAINING VESSEL JOINED INDIRECT HEAT CONTACT WITH SAID BLOCK AT ONE OF SAID RESPECTIVE SIDES FORHEAT EXCHANGE WITH SAID BLOCK, A RELATIVELY THINWALLED VACUUM CONTAINERIN WHICH SAID BLOCK AND SAID TWO VESSELS ARE MOUNTED IN SPACED RELATIONTO THE CON-